I agree with you — inconsistency is maybe Arsenal's biggest problem and one of the reasons why they haven’t won anything in the last five years.
The main reason why Arsenal have been ending the season in second position is just inconsistency, Arsenal are always having chances to win the league title, but their performance is always dropping. Mostly Arsenal will start the season well, and everyone will think they will be able to win the premier league title that season, but before the season ends, you going to see that Arsenal will start losing matches that they are not suppose to lose, I don’t really know why thats always happening to Arsenal, but with the new signs which they just made, let’s hope next season is going to be a different season for them.
Arsenal are very good at breaking hearts, there second name is inconsistency but there is something I have observed about them. I'm not sure if it's the effort they put in playing from the beginning of the season, it's towards the end of the season or in the middle they do lack this consistency, they don't do it in the beginning, they usually stand toe to toe with any team or even sometime be at the top of the table until they begin to fall down.
What I observed during this period is injuries, if happened last two seasons and it's happened this season that just pass again. However, I have notice they came loaded with this season with different players, I believe they are going to have sufficient players enough to lead them to the promise land. Gabriel has been a failure for them, maybe Gyokores will patch that place and even do better than this before. Arsenal really deserved a the trophy now or never.